Odd colour pick with dark theme about ponpokodiff

[nexus6-haiku]

It's slightly different than #17 but related.

[humdingerb]

The text becoming black on resize is #17 , I'd say.
The main issue of the illegibility is due to the fixed colour scheme. I just checked with black and white text, the colours look good with that. But your text colour is a 'darkish' light blue, which doesn't work well with the chosen colours for a dark theme.
We'd need a nice algorithm to choose a good red, yellow, green colour for a given text colour. (And of course a fix for #17...)

Another confusing thing is that the empty space ("colorEmpty") appears always light grey. It uses B_PANEL_BACKGROUND_COLOR, which should be dark in a dark theme, but doesn't appear to change...

[nexus6-haiku]

Due the lack of a proper and official dark mode on Haiku, We'd need a System-wide algorithm to determine if we are on a dark-ish theme by checking the relevant components, I presume. I.e. if the background colour is on a bright tone and the foreground text colour on the dark end of the spectrum then maybe there's a dark theme in place.
At that point PonpokoDiff or any other app might pick the most appropriate built-in palette.
It's a bit simplistic and yours looks the right way to do it, by the way. A bit more complex, though.

[pulkomandy]

There is a perceptual_lightness function that can be used, if it is higher than 127, the color is "light". This is what we use for the desktop icons text color for example (to make sure the color of the text is always visible on top of the background color)

[nexus6-haiku]

amazing, this is exactly what every app should use to adjust custom colours to match the system theme. Thanks!

[humdingerb]

Appreciated. I'll use perceptual_lightness instead of the simple if (bkColor.Brightness() > 100).

That doesn't solve using colours that provide enough contrast with the current text colour. We'd need something like:

rgb_color textColor = ui_color(B_DOCUMENT_TEXT_COLOR);
rgb_color lightColor = {163, 255, 180, 255};
rgb_color darkColor;
darkColor = find_contrasting_color(lightColor, textColor);

That is, find_contrasting_color() should find the equivalent of the fixed lightColor that has a nice contrast to the current textColor.

Anyway, here's a suggestion for better contrasting colours for the MoonFlat light blue colour:

WRT using the loopy Invalidate(), I'd rather we find and fix the underlying issue... :)
Until then, dark theming user will have to wave a window in front. :)

[pulkomandy]

If you just need a green or a red, you can use one of the HSV or HSL colorspaces, where the color can be selected separately from the brightness.

Here is an example in Renga using the HSLUV colorspace: https://github.com/pulkomandy/Renga/blob/master/ui/hsluv.c#L214

you can set H and S to colors that look nice (S should be high, H should be whichever value gives a red or green), and then set L to a low value for a dark color, and a large value for a light color. The use the linked function to convert to RGB.

Or you can simply pick a light and a dark green, a light and a dark red, and switch between the two color sets depending on perceptual_lightness of the background color.

Or yet another way is to mix the colors:

newRed = background.red + lDeletedColor.red / 2;
newGreen = background.green + lDeletedColor.green / 2;
newBlue = background.blue + lDeletedColor.blue / 2;

This gives you a color that is "in between" your background and your "deleted color" (a base red). On a dark background this will be a dark color, on a light background this will be a light color, but it will preserve the red or green-ness of the initial color.

[humdingerb]

Or you can simply pick a light and a dark green, a light and a dark red, and switch between the two color sets depending on perceptual_lightness of the background color.

That's what I do now.
Thanks for the hint for mixing colours etc. I don't want to complicate things too much. I originally just didn't think about people using quite less bright text colours in their dark theme. My dark background colours therefore were a bit too bright. I've now toned them down some more with PR #19.
@nexus6-haiku, think those colours are OK?